1. Field of the Invention
The present invention relates generally to vehicle seat occupant sensing systems and, more particularly, to a vehicle seat frame assembly having at least one flat washer style load cell packaged in the Federal Motor Vehicle Safety Standards (FMVSS) 207/210 load path for sensing the presence, weight, and/or center of gravity of a seat occupant.
2. Background Art
Vehicles such as automobiles are equipped with seat occupant sensing systems and safety devices such as air bags and seat belts to protect seat occupants. Typical seat occupant sensing systems provide a sensing output indicative of the seat occupant such as the weight of the occupant. Safety devices associated with a seat may be controlled as a function of the sensing output. For example, if a seat occupant sensing system senses that the weight of a seat occupant is indicative of a child occupying the seat, then a safety device such as an air bag associated with the seat may be deployed with less force than if the seat occupant is an adult. Furthermore, if the seat occupant sensing system senses that a seat is unoccupied, i.e., senses that there is no weight on the seat, then the safety device associated with the seat can be deactivated.
Some typical seat sensing systems include load cells having a cantilever or bridge style instrumented with a strain gage. A problem with such loads cells is that they do not provide optimal loading conditions in the FMVSS 207/210 load path because the strain gage substrate must be robust enough to resist the FMVSS 207/210 load or an additional bracket must be used to resist the FMVSS 207/210 load after the strain gage substrate deforms.
What is needed is a seat sensing system having a load cell which can be packaged in the FMVSS 207/210 load path without having to resist the FMVSS 207/210 load in a vehicle seat frame assembly. Such a load cell would include a flat washer style load cell and a primary load carrying member such as a fastener passing through the load cell to clamp upper and lower seat frame members together. The fastener would bear the brunt of the FMVSS 207/210 load and, as a result, the flat washer style load cell would not be required to manage the FMVSS 207/210 load.
It is an object of the present invention to provide a seat frame assembly having at least one flat washer style load cell positioned in the FMVSS 207/210 load path for sensing the presence, weight, and/or center of gravity of a seat occupant.
It is another object of the present invention to provide a seat frame assembly having at least one flat washer style load cell positioned between upper and lower seat members at a level underneath the seat belt restraint attachment of the seat for sensing the presence, weight, and/or center of gravity of a seat occupant.
It is a further object of the present invention to provide a seat frame assembly having a flat washer style load cell positioned between upper and lower seat members at each corner of the seat at a level underneath the seat belt restraint attachment of the seat for sensing the presence, weight, and/or center of gravity of a seat occupant.
It is still another object of the present invention to provide a seat frame assembly having a flat washer style load cell and a primary load carrying member such as a fastener passing through the load cell to join upper and lower seat members together with the load cell interposed between the seat members at a level underneath the seat belt restraint attachment of the seat for sensing the presence, weight, and/or center of gravity of a seat occupant.
It is still a further object of the present invention to provide a seat frame assembly having a flat washer style load cell and a primary load carrying member such as a fastener passing through the load cell to join upper and lower seat members together with the load cell interposed between the seat members and positioned in the FMVSS 207/210 load path for sensing the presence, weight, and/or center of gravity of a seat occupant.
It is still yet another object of the present invention to provide a seat frame assembly having a flat washer style load cell positioned between upper and lower seat members at a level underneath the seat belt restraint attachment of the seat for sensing the presence, weight, and/or center of gravity of a seat occupant in which each load cell is packaged in the FMVSS 207/210 load path without having to resist the FMVSS 207/210 load.
It is still yet a further object of the present invention to provide a seat frame assembly having a flat washer style load cell and a fastener passing through the load cell to join upper and lower seat structural members together with the load cell interposed between the seat members at a level underneath the seat belt restraint attachment of the seat for sensing the presence, weight, and/or center of gravity of a seat occupant in which the joining operation of the fastener is terminated at a predetermined joining force.
Yet, it is still another object of the present invention to provide a seat frame assembly having a flat washer style load cell and a spring positioned between upper and lower seat members at a level underneath the seat belt restraint attachment of the seat such that the spring imparts a predetermined pre-load on the load cell for improving the load cell""s ability to sense the presence, weight, and/or center of gravity of a seat occupant.
Yet, it is still a further object of the present invention to provide a seat frame assembly having a flat washer style load cell, a spring, and a primary load carrying member such as a shoulder bolt passing through the load cell and the spring to join upper and lower seat members together with the load cell and the spring interposed between the seat members and positioned in the FMVSS 207/210 load path such that the spring imparts a predetermined pre-load on the load cell for improving the load cell""s ability to sense the presence, weight, and/or center of gravity of a seat occupant.
In carrying out the above objects and other objects, the present invention provides a seat frame assembly for a vehicle. The seat frame assembly includes a seat portion and a seat back connected to the seat portion. An upper track is positioned beneath the seat portion and connected to the seat portion. A lower track is positioned beneath the upper track. The upper track and the lower track engage with one another such that the upper track is movable with respect to the lower track in order to move the seat portion and the seat back in a longitudinal direction with respect to the lower track.
A seat belt restraint attachment is positioned underneath the seat back between the seat portion and the upper track and connected to the upper track. A riser is positioned on a vehicle floor beneath the lower track. A flat washer style load cell is interposed between the lower track and the riser at a level below the seat belt restraint attachment. A fastener such as a shoulder bolt extends through the load cell and mounts the lower track to the riser. The load cell generates a sensor signal indicative of the weight of an occupant of the seat portion. The sensor signal may be processed to determine at least one of the presence, weight, and/or center of gravity of the occupant of the seat portion.
The seat frame assembly may further include a spring such as a wave washer, a piece of rubber, or the like interposed between the load cell and at least one of the lower track and the riser. The fastener extends through the spring and the load cell and mounts the lower track to the riser. The spring imparts a predetermined load on the load cell when the fastener mounts the lower track to the riser. The load cell takes into account the predetermined load when monitoring the weight of an occupant of the seat portion in order to enhance the resolution of the load cell.
The advantages of the present invention are numerous. For instance, the flat washer style load cell and associated fastener are packaged in the FMVSS 207/210 load path at a level beneath the seat belt restraint attachment thereby eliminating the need for a seat belt tension sensor. The fastener bears the brunt of the load on the seat thereby freeing the flat washer style load cell from having to manage the load. Further, in a second embodiment, a spring imparts a predetermined load on the flat washer style load cell when the fastener is tightened down. As a result, a relatively lighter duty load cell may be used which translates into a more cost effective and higher resolution system.
The above objects and other objects, features and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.